Bisphenol A has a chemical name of 2,2-di(4-hydroxyphenyl)propane, and is widely used as raw materials in industry, for example, it can be used to produce epoxy resin and polycarbonate, etc.
Bisphenol A can be synthesized by dehydration-condensation of excessive phenol and acetone in the presence of an acidic catalyst, and the specific reaction formula is as follows.

This reaction is an exothermic reaction. In an adiabatic fixed bed reactor, if there is no effective heat-removing means, the temperature in the reactor may rise significantly, while the current cation exchange resin as condensation catalyst may be inactivated under high temperature and side reactions may be enhanced at the same time. Thus, a plurality of cooling streams would be needed to prevent the temperature rise within an adiabatic fixed bed reactor.
For example, Chinese patent application CN1390819A discloses a method for producing bisphenol A, wherein the dehydration-condensation is conducted in an adiabatic fixed bed reactor, and two catalyst beds are provided in the reactor, wherein a portion of reaction mixture as cycled  stream is received between said two catalyst beds, mixed with a feed stream to the reactor, and transferred into the upper portion of the reactor. The residual portion of the reaction mixture is discharged from the reactor and transferred into a distillation system, where the fraction of acetone-water-phenol is distilled out, and the resultant residue is crude bisphenol A, which is melted and crystallized progressively to obtain bisphenol A product. The drawback of this method is that the cycled stream is not dewarted, thus the water content in the reaction stream is high and adverse to the reaction obviously.
CN1406218A discloses a method for producing bisphenol A, which comprises charging phenol and acetone into a multistage reactor, wherein at least two adiabatic fixed bed reactors charged with cation exchange resin are arranged in series, a heat exchanger is provided at the inlet of each reactor in order to control the temperature within each reactor at a level of not greater than 90° C. However, this patent application merely points out that a heat exchanger is provided at the inlet of each reactor in order to control the reaction temperature, and no specific controlling means is mentioned in its specification and examples.
At present, cation exchange resin is the most widely used condensation catalyst; the resultant reaction stream is concentrated to remove the generated water, unreacted acetone and part of phenol; and then the concentrated reaction stream is transferred into post-treatment procedures such as crystallization, etc. to obtain bisphenol A product finally, wherein the unreacted phenol and acetone may be recovered and cycled back to the reaction system.
Qi xiwang and Chen Hongfang reported (Petrochemical Industry, 1996, 25(9):620-624): water is a strong poison for sulfonic acid type acidic ion  exchange resin catalyst, and this may be explained as that a relatively firm hydrogen bond network may be formed between the water generated in the reaction and the sulfonic acid groups on the catalyst's framework and said network occupies the active catalytic sites, thus may inhibit the catalytic activity significantly. Thus, the lower the water content in the reaction stream, the more favored the reaction. In addition, water is one of reaction products, so its removal may promote the reaction forwardly.
Therefore, many studies have been conducted on how to remove the water generated in the reaction.
CN1118155A, CN1077187A and CN1080914A all mention that a condensation is conducted in a multistage suspended bed reaction column, and a stream of inert gas is fed at the bottom of the reactor to remove the water generated in reaction by gas stripping. Then, without concentration, the reaction stream is directly crystallized to form an adduct crystal of bisphenol A and phenol and a liquor. After solid-liquid separation, bisphenol A is obtained by removing phenol from the adduct crystal. However, the drawbacks of these methods lie in that the multistage suspended bed reactor has a complex structure and is difficult to construct, and many other devices may be needed to treat and cycle the inert gas at the same time.
U.S. Pat. No. 5,087,767 discloses a method for preparing bisphenol A, wherein part of the water generated in reaction is removed through a pervaporation from the reaction mixture containing phenol and acetone, wherein said pervaporation is performed by a selective water-permeable membrane, such as porous glass membranes, porous silica membranes, porous alumina membranes and porous ceramics membranes. According to said method, the water generated in reaction may be quickly removed by pervaporation simultaneously or alternatively as the reaction occurs so that high conversions of acetone and  phenol and a high yield of bisphenol A are achieved. However, its drawback is that the capacity of separating water is limited. In addition, this method is merely suitable for a batchwise stirred reactor rather than a continuous fixed bed reactor.